Liam Hockley

Current Research Projects:

I am currently in my first year of my PhD, with the prospective thesis title Baryonic Resonances in Hamiltonian Effective Field Theory and Lattice QCD.

In a nutshell, my research is aimed at better understanding the structure of excited states of low-lying baryons such as the nucleon and the Delta. Historically the nucleon case has been particularly challenging since the parity of its first excited state contradicts the expected parity from a harmonic oscillator model for a state composed of 3 quarks. Recent work by the University of Adelaide suggests that rather than taking this first excited state (known as the Roper resonance) to be a naive 3-quark state, one should instead adopt the model of a state generated dynamically through various scattering channels. I'm hoping to verify this interpretation by studying the similarly troublesome excited states of the Delta baryon.

The initial aim of this work is to compare the mass spectrum of the Delta resonances obtained through both Lattice QCD and Hamiltonian Effective Field Theory (HEFT) in order to comment on the Delta(1600) as being a dynamically generated resonance. To realise this, we will construct an effective Hamiltonian involving several relevant scattering channels for the Delta(1600), namely: pion-nucleon, pion-Delta(1232) and sigma-Delta(1232). We will then look to solve the Hamiltonian for its eigenstates and thus produce an energy spectrum for the Delta resonance. If it is found that this spectrum is comparable to that generated via Lattice QCD, this would corraborate similar findings for the historically troublesome Roper resonance.

Previous Research Projects:

Other than my current work in hadronic physics on the lattice, I also have an interest in the role CP violation plays in understanding the matter-antimatter imbalance in the universe. My Masters thesis title was Direct CP Violation in B Meson Decays, and I specifically focused on the CP violation effects in B->K+ K- pi decays. In order to calculate direct CP violation in these decays, I calculated the CP asymmetry arising from the interference between relevant tree and penguin diagrams. I employed well known tools such as Effective Hamiltonians and Naive Factorisation Approximations to do this. The first of these methods allows one to describe the amplitudes of particle decays in terms of products of quark currents in the Operator Product Expansion, while the second provides the means for simplifying the resultant matrix elements. One then calculates these matrix elements using form factors for which we took well known models.